J. OLDS AND M. E. OLDS I75 



The most striking cases were of the hrst type (Figs. 17 and 20 I, II, IV). 

 They were recorded mainly from areas such as the dentate gyrus, tmibria 

 regions, and mammillo-thalamic tract regions, which appeared to be 

 'seizure-prone' in our previous experiment (Fig. 10). In these cases, the 

 unit was originally responding in a sporadic pattern with single responses 

 or groups appearing at less than one per second. Stimulation when 



-M'3 1/3 )0°P Before Stimulation #1118 Dentate 



» |i 1 ,4 i i ji iiiiiii X" i< » r» i ii^i 4» ' ' ' *"'4 ''' ' 4* ***'**'''*'**^^ 



^ tf tt ^ ni i < i w i 4i III ! »■ ' iiWMw«4«*«wlN4>'i«^«"y ^ 



After 5' Stimulation No RemforcemenI 



-A- A ^ ' - - 



ii» i A y i 4 I t ■» n il 11 * 1 ■« |>| » I'i i iii f il i i |< '< > M Jii j i N 



'<| iii i^i 4 ii 4 mu iumm^immmmmmmmmmm m itt ifi ii » iiii|iiili > i>i w > rt» i M«ii iii 1 ■ i nwi^i u 



After 5 Reinforcoment 



mimitm4'»tm^mmmtm$»tmmm*mi»^^ ^ i :i i i i i i4 M ii«iiiii » ii i i» #i 



iii i iii i | iw i i ^ i i ' i j' i wii^ii I' ^m ' j iii i i iii i ii u I I Ai li \\ i \ n $\\ i «i i i 4 ii i 



Fig. 17 

 E.xperimciit on single-unit response recorded from dentate gyrus. Small unit response 

 (almost lost among larger slow waves) occurs at rate of approximately one per second 

 tefore stimulation, and rate is not greatly increased by uncorrelated stimulation. 

 When stimulation is correlated as reinforcement for unit response, however, continuous 

 firing (at rate of about 30 per second) ensues. Time base as in Fig. 18. 



nitrociuced during silent peru)ds did not cause any elicited tiring. Such 

 stimulation could be continued for periods of 5 minutes or more without 

 materially augmenting the response rate. Then, if the stimulation was 

 withheld and delivered only after the appearance of a single or grouped 

 response, ten to twenty reinforcements would often suffice to cause a 

 sudden burst of activity; the unit would respond continuously at rates as 

 high as 30 per second. This burst would sometimes last for a period of only 



